[ANNOUNCE] ngx_echo v0.31: more sequential subrequest fixes inspired by ngx_srcache

[agentzh]

Hi, all~

I'm glad to release ngx_echo v0.31 which include various fixes on
sequential subrequests inspired by the ngx_srcache development:

    http://github.com/agentzh/echo-nginx-module/tarball/v0.31

Here's the (boring) change log:

    *  the echo wev handler should not proceed if it is still waiting
for some sequential subrequest or has just processed one to avoid
bouncing issues.
    * fixed a segfault for echo_exec for 0.7.x: we should check
r->done before proceeding.
    * no longer explicitly set r->write_event_handler to
ngx_http_request_empty_handler because it's totally wrong for the
state machine.
    * fixed the sequential subrequest model bugs: we should ensure the
pr->write_event_handler gets called immediately after the
post_subrequest callback when the subrequest finalizes (the
ngx_http_post_request function always pushes requests at the *end* of
the r->posted_requests queue).

ngx_srcache is near the corner of its first public release:

    http://github.com/agentzh/srcache-nginx-module

calio++ is currently working on the last missing bit in it, i.e.,
response headers caching :)

Cheers,
-agentzh